1. Field of the Invention
The present invention relates to a multilayer substrate, a component mounted board, and a method for producing a component mounted board.
2. Description of the Related Art
Among past inventions relating to multilayer substrates, for example, a semiconductor mounting method disclosed in Japanese Patent Application Publication No. 2006-120683 is known. In the semiconductor mounting method, bumps of a bare semiconductor chip are bonded to wires of a flexible wiring board, which includes films of liquid crystal polymer, by ultrasonic flip-chip bonding. By applying ultrasonic vibration to the semiconductor chip in a direction substantially the same as the alignment direction of the liquid crystal polymer, the wires and the bumps are bonded together.
However, since the flexible wiring board is flexible and likely to deform, it is difficult to mount the bare semiconductor chip to the flexible wiring board securely by the semiconductor mounting method disclosed in Japanese Patent Application Publication No. 2006-120683. More specifically, the bare semiconductor chip may include a dense-bump region where bumps are distributed densely and a sparse-bump region where bumps are distributed sparsely. In this case, the flexible wiring board includes a dense-wire region where wires which the bumps are to be bonded to are distributed densely and a sparse-wire region where the wires are distributed sparsely.
In this case, the deformability of the flexible wiring board differs between the wire-dense region and the wire-sparse region. When ultrasonic vibration is applied to the semiconductor chip, the semiconductor chip is pressed against the flexible wiring board, and the amount of deformation differs between in the wire-dense region and in the wire-sparse region. Accordingly, the condition of bonding of the wires to the bumps differs between in the wire-dense region and in the wire-sparse region. Thus, it is difficult to mount the bare semiconductor chip to the flexible wiring board securely.